Collector means for solar energy collecting system

ABSTRACT

In accordance with the present invention, an improved collector means for a solar energy collector system having an absorber plate and a glazing panel spaced from at least one side of the absorber plate in which a cap means is coupled to and extends along one edge of the absorber plate and a depending leg extends over the complimentary edge of the glazing panel, the cap means having formed therein at least one air channel conforming in shape to the cross-sectional shape of the cap means and having air inlet means adjacent the bottom of a leg of the cap means in communication with the channel and an air outlet means adjacent the top of the cap means and in communication with the channel and adapted to permit currents of cooling air to pass therethrough from the inlet to the outlet, thereby maintaining said complimentary edge of the glazing panel relatively cool. In a preferred embodiment, the improved collector means is mounted edgewise adjacent the bottom of a parabolic trough-type reflector means and has a glazing panel on both exposed sides thereof. In accordance with a further embodiment of the present invention, the glazing panel is a flexible sheet material detachably coupled adjacent one edge of the absorber plate and the other end of a glazing material comprises a supply roll mounted adjacent the other edge of the absorber plate, whereby a fresh surface of glazing sheet material can be withdrawn from the roll and mounted parallel to the absorber plate as needed. Preferably, the roll of glazing sheet material is spring loaded so as to maintain the material taut, for example by a window shade-type roll means.

The present invention relates to solar energy collecting systems andparticularly to solar energy collecting systems of the non-tracking,focused type. More particularly, the present invention relates to animproved collecting means for solar energy collecting systems.

BACKGROUND OF THE INVENTION

Broadly, solar energy collecting systems include a collecting meanswhich receives the solar energy and converts it to a useful form. Inmost energy collecting systems a receiving, focusing or reflecting meansof some type receives the sun's rays from a predetermined extended areaand directs the received solar energy to a collector means of some typewhich, in turn, receives the initial energy in an enhanced orconcentrated form, specifically at a much higher degree of heat per unitarea than originally received by the receiving means. The collectormeans utilizes the energy which it receives to heat a fluid, such as airor water, directly for immediate use or stores the same in a heat sumpor heat reservoir for ultimate use on demand. The heat energy receivedby the collector may also be converted to electrical energy forimmediate use or converted to electrical energy and stored in storagedevices or batteries for ultimate use on demand.

Most solar energy systems, in use or proposed for use, have been of thetype in which an extended reflecting surface receives the solar energyand directs it to a substantially smaller collector means. Suchreflecting surfaces may also take a wide variety of forms. For example,flat, dished, parabolic troughs, etc. The system may also be of thetracking or nontracking type, which, to a great extent, depends upon thereceiving surface. For example, flat receiving surfaces or reflectingsurfaces need to be oriented at all times according to the position ofthe sun in order to receive sufficient energy. Thus, such systems areso-called tracking systems when the receiving surface tracks themovement of the sun from horizon to horizon on a daily basis and,preferably, the azimuthal position of the sun on a seasonal basis. Whiletracking on a seasonal basis can be performed manually, it is whollyimpractical to manually track the sun on a daily basis. Accordingly,automatic tracking systems are provided. Such tracking systems arecomplex and expensive to operate and maintain. By contrast, a parabolictrough-type receiving means can be utilized as a so-called nontrackingsystem. By appropriately shaping the parabola, sizing and positioning acollector within the parabola so as to receive substantially all of theenergy striking and reflected by the inner reflecting surface of theparabola and correctly positioning the reflector surface in a generallyeast-west direction, it is unnecessary to track on a daily basis and allthat is required for maximum efficiency is changing the orientationseveral times, for example, two to four times per year, to accommodateseasonal changes of the positions of the sun.

The collector means for solar energy systems either receives solar raysdirectly, or as previously pointed out, indirectly from a receiving,focusing or reflecting means. The basic component of the collectingmeans comprises an absorber means which is generally a panel orplate-type device adapted to absorb the collected solar energy andconvert it to an immediately useful form or a form which can be storedfor use on demand. For this purpose, the absorber means is constructedof a material adapted to absorb the heat and, to the extent possible,retain the absorbed heat, often being a black body or a body having acoating of black paint as opposed to a reflective body. In a majority ofinstances the absorber means is a flat plate-type heat exchanger. Heatexchange is carried out by forming fluid passages such as rectangularducts, tubular ducts and the like through which a heat exchange mediumis flowed. In order to shield or insulate the exposed side or sides ofthe absorber means against heat losses through conduction and convectionand/or cooling by the wind, it is conventional practice to mount atransparent plate or sheet adjacent the exposed side of the absorberplate and spaced therefrom so as to form an essentially dead air spacebetween the absorber plate and the shielding plate. Thus, the shieldingor insulating plate will transmit solar energy therethrough to theabsorber plate, while at the same time preventing direct contact by thewind, and heat losses from the absorber plate by conduction andconvection. Generally, the shielding or insulating plate is a polymericmaterial of some type such as polyethylene, polyvinylchloride, etc. andmay be in the form of a rigid or semirigid plate or a flexible sheetmaterial. Regardless of the structure of the shielding or insulatingpanel or panels, the most serious problem encountered is rapiddeterioration of the panels, usually because of the high degree of heatconcentrated in the absorber plate and the mounting which requires someconnection between the absorber plate and the shielding panel. Thus,there is the need for frequent replacement. Hence, it is necessary thatthe shielding or insulating panel be mounted so as to not contact theabsorber plate. However, regardless of the manner of mounting, there isstill the problem of the shielding panel eventually deteriorating andrequiring replacement because of radiated heat and conducted heatthrough the connecting means. This is particularly true in the case ofpanels of flexible polymeric materials. While such panels are usuallystretched taut and are often of material which will shrink to thusfurther tighten the same, there is still a tendency for the wind toforce the material into contact with the absorber plate or for thematerial to lose its resiliency and sag into contact with the absorberplate. Thus, it is highly desirable that some means of maintaining theshielding or insulating panel, often referred to as "glazing",relatively cool, preventing contact with the absorber plate andproviding some means for rapidly replacing deteriorated panels.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view, partially in section, of a solar energycollector system in accordance with one embodiment of the presentinvention.

FIG. 2 is an end view of the system of FIG. 1.

FIG. 3 is a perspective view, partially in section, of an improvedcollector means in accordance with the present invention; and

FIG. 4 is a cross-sectional view, partially in section, of the collectormeans of FIG. 3.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide animproved solar energy collecting system which overcomes theabove-mentioned and other problems of the prior art. Another object ofthe present invention is to provide an improved collector means for asolar energy collection system which overcomes the above-mentioned andother problems of the prior art. Yet another object of the presentinvention is to provide an improved collector means for a solar energycollector system which is relatively inexpensive to manufacture andinstall. A further object of the present invention is to provide acollector means for a solar energy collector system, including at leastone glazing or insulating panel. Another and further object of thepresent invention is to provide a collector means for a solar energycollector system in which deterioration of an insulating or glazingpanel is reduced. Yet another object of the present invention is toprovide a collector means for a solar energy collector system in whichan insulating or glazing panel is maintained relatively cool. Yetanother object of the present invention is to provide an improvedcollector means for a solar energy collector system having an improvedinsulating or glazing panel of flexible material. A still further objectof the present invention is to provide an improved collector means for asolar energy collector system which can be readily mounted within thecollector means. Another and further object of the present invention isto provide an improved collector means for a solar energy collectorsystem in which an insulating or glazing panel can be readily replacedin the event of deterioration. These and other objects and advantages ofthe present invention will become apparent from the followingdescription.

In accordance with the present invention, an improved collector meansfor a solar energy collector system, having an absorber plate and aglazing panel spaced from at least one side of the absorber plate, isprovided in which a cap means having a depending leg is coupled to andextends along one edge of the absorber plate and extends over thecomplimentary edge of the glazing panel, the cap means having formedtherein at least one air channel conforming in shape to thecross-sectional contour cap means and having air inlet means adjacentthe bottom of the leg of the cap means in communication with the channeland an air outlet means adjacent the top of the cap means and incommunication with the channel and adapted to permit currents of coolingair to pass therethrough from the inlet to the outlet, therebymaintaining said complimentary edge of the glazing panel relativelycool. In a preferred embodiment, the improved collector means isU-shaped and is mounted edgewise adjacent the bottom of a trough-typereflector means and has a glazing panel on both exposed sides thereof.In accordance with a further embodiment of the present invention, theglazing panel is a flexible sheet material detachably coupled adjacentone edge of the absorber plate and the other end of the glazing materialcomprises a supply roll mounted adjacent the other edge of the absorberplate, whereby a fresh surface of glazing sheet material can bewithdrawn from the roll and mounted parallel to the absorber plate asneeded. Preferably, the roll of glazing sheet material is spring loadedso as to maintain the material taut, for example by a window shade-typeroll means.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The nature and advantages of the present invention will be betterunderstood by the following description when read in conjunction withthe drawings.

FIG. 1 of the drawings illustrates a preferred solar energy collectorsystem, in accordance with the present invention, which comprises aparabolic trough-type reflecting surface which can be fixedly installedin a generally east-west direction to provide a nontracking system. Aspreviously indicated, better year around efficiency can be attained byadjusting the reflector surface several times per year, for example, twoto four times per year, to compensate for changes in the position of thesun due to seasonal changes. The general design, structure, installationand operation of this type of system is disclosdd in greater detail inU.S. Pat. Nos. 4,024,852 and 4,263,892, which are incorporated herein byreference, and other such details are known to those skilled in the art.

In accordance with FIG. 1, a parabolic trough-shaped extended reflectorsurface 10 is mounted on legs 12, which are, of course, anchored, as inconcrete. Further anchoring is provided by struts or guy wires 14, whichare in turn attached to anchors 16, also mounted in concrete or otherfoundation material. Reflector surface 10 is made up of an open framemember 18, which defines the perimeter of the reflective surface andincludes a plurality of curved supports 20, 22, and 24 of semi-paraboliccurvature. Mounted between supports 20 and 22 of frame means 18 are aplurality of elongated, flexible strips of reflective material. Strips26 are mounted in parallel relationship to one another and lengthwisewith respect to the parabolic trough, so as to form an essentiallycontinuous reflector surface. The parallel relationship of strips 26 maybe abutting or overlapping, as necessary or desired. A like plurality ofreflector strips 28 are mounted between supports 22 and 24. Mountedalong the bottom center of parabolic trough 10 is a collector means 30.Reflecting surface 10 is preferably mounted on support legs 12 throughend rods 32, which permit rotation of the system to compensate forseasonal variations in the location of the sun.

FIG. 2 is an elevational end view of the system of FIG. 1.

FIG. 3 of the drawings is an isometric view, partially in section, ofthe improved collector means 30 of the present invention. Collectormeans 30 includes absorber plate means 32, which, as indicatedpreviously, is preferably mounted edgewise or in an upstanding manneradjacent the bottom of a parabolic trough-type reflector. Formed inabsorber plate 32 are tubular passages 34 for carrying a heat exchangefluid, such as air or water. Tubular passages 34 may be appropriatelymanifolded at the ends thereof so that heat exchange medium may beflowed therethrough. Absorber plate 32 is made of a heat absorbingmaterial, for example, may be extruded or pultruded from aluminum. Thebottom edge of absorber plate 32 is fixedly attached to a base 36 whichpreferably is a section of parabolic trough 10 (FIG. 1). Fixedly mountedto the top edge of absorber plate 32 is a mounting channel 38. Mountingchannel 38 provides means for mounting cap means 40 and glazing sheets42. As illustrated, cap means 40 is provided with a downwardly extendingrib 44, which slides into a slot in mounting channel 38. In accordancewith one embodiment of the present invention, glazing panels 42 are atransparent, flexible sheet material, such as polyethylene film. Byutilizing a thin film, the cost of construction can be substantiallyreduced and, as hereinafter pointed out, the surfaces of the glazingpanels may be readily replaced. For example, a polyethylene filmapproximately 5 mils thick will generally have a strength in the rangeof about 20,000 to about 40,000 psi, which when properly mounted andmaintained, adequately serves the purposes of a glazing panel. In orderto mount glazing panels 42, V-shaped channels 46 are fixedly mountedonto the sides of mounting channel 38. V-shaped channels 46 need notextend the entire length of the unit, but may be spaced at appropriatepoints along the length. Alternatively, tabs may be punched frommounting channel 38 to provide a plurality of V-shaped supports. Hookedinto channels 46 are support channels 48 which terminate at the lowerends in a U-shaped receiving channel 50. The upper end of the glazingpanel 42 is detachably mounted in receiving channels 50. As illustrated,the glazing sheet 42 is simply wrapped around rectangular rods 52, whichfit into channels 50 in such a manner that they will become wedged inchannels 50 when a downward tension is applied to glazing sheet 42. Theglazing sheet 42 is simply wrapped around the rods 52. The lower ends ofglazing panels 42 terminate in rolls or glazing panel material mountedon spring-loaded window shade-type rollers 54. Rollers 54 keep glazingpanels 42 taut at all times. However, should a portion of or all ofglazing panels 42 deteriorate, the upper ends of the panels may simplybe removed from the channels 50, the deteriorated portion removed, ifnecessary, a fresh surface mounted on rods 52 and the rods reinserted inchannels 50. Thus, the structure explained not only maintains theglazing panels 42 taut at all times but also provides ready replacementof the surfaces thereof. While the cap means 40 is preferred, it is notnecessary in all cases and mounting channel 38, V-shaped channels 46 andchannels 48 could be replaced by an appropriate mounting means ofanother type. In addition, in such cases, the window shade-type rollers54 could simply be rotatable rollers and the upper ends of glazingpanels 42 could be detachably mounted on absorber plate 32 by means of awide variety of biasing or spring-type mounting means. Cap means 40 alsohas formed thereon an upstanding rib means 56 whose function will beexplained with reference to FIG. 4. Downwardly, depending legs 58 ofU-shaped cap 40 should extend over the mounting for glazing panels 42.

Irrespective of the manner of mounting the upper ends of glazing panels42 to absorber plate 32, heat will be transmitted through the mountingmeans to the glazing panels causing damage and deterioration thereof.Accordingly, in accordance with another embodiment of the presentinvention, U-shaped cap means 40 provides a means of cooling the glazingpanel mounting means and the upper ends of the glazing panels asillustrated in FIG. 4. Downwardly depending legs 58 of cap means 40 andthe horizontal portion of the cap means 40 are hollow to provide atleast one air channel 60. In the preferred embodiment, legs 58 areprovided with a pair of air channels 62 and 64, respectively.Communicating with air channels 62 and 64 are air inlets 66 and 68,respectively, and communicating with air channel 60 are air outlets 70.Channels 66, 68 and 70 provide gravity thermal draft channels in capmeans 40 which serve to cool the mounting means for the glazing panelsand the top of the glazing panels. As temperature builds up adjacent theupper end of the glazing panels, thermal convection drafts accelerate inchannel 62. As channel space 62 begins to heat up, thermal draftcurrents begin to flow through channel 64. Accordingly, hightemperatures, which could be as high as 700° F. during stagnation, areprevented from reaching the glazing panels 42. Legs 58 of cap 40 arealso preferably spaced about 1/4 inch from channels 48 to allow ambientair to circulate, thus further aiding in the prevention of hightemperatures reaching the glazing panels 42.

While specific materials, items of equipment, construction of equipmentand modes of operation have been set forth above, it is to be understoodthat these specific recitals are by way of illustration and to set forththe best mode in accordance with the present invention only and are notto be considered limiting and that substitutes, equivalents, variationsand modifications thereof will be apparent to one skilled in the artwithout departing from the present invention.

That which is claimed:
 1. Collector means for a solar energy collectorsystem including an absorber plate means having at least one sidethereof exposed to solar rays, comprising:(a) a transparent flexibleglazing sheet mounted generally parallel to the exposed side of saidabsorber plate and spaced therefrom; (b) one end of said glazing sheetbeing detachably coupled to said absorber plate adjacent one edge ofsaid absorber plate. (c) the other end of said glazing sheet comprisinga supply roll of glazing sheet material mounted adjacent the other edgeof said absorber plate; (d) whereby fresh glazing sheet material can bewithdrawn from said supply roll and mounted parallel to said absorberplate as needed; and (e) cap means coupled to and extending along oneedge of said absorber plate and having a downwardly depending legextending at least partially over the complimentary edge of said glazingsheet and spaced therefrom; (f) said cap having formed therein at leastone air channel generally conforming in shape to the cross-sectionalshape of said cap, including air inlet means adjacent the bottom of saidleg of said cap and in communication with said channel and air outletmeans adjacent the top of said cap and in communication with saidchannel and adapted to permit currents of cooling air to passtherethrough from said inlet to said outlet.
 2. Collector means inaccordance with claim 1 wherein the absorber plate is mounted so as toexpose both sides thereof to solar rays, like glazing sheets are mountedon both sides of said absorber plate and the cap is an invertedgenerally U-shaped cap with the depending legs thereof extending atleast partially over the edges of said flexible glazing sheets. 3.Collector means in accordance with claim 1 wherein the channel includestwo parallel channels in at least the depending leg portion thereof. 4.Collector means in accordance with claim 1 wherein at least one edge ofthe glazing sheet is spring biased to maintain said glazing sheet taut.5. Collector means in accordance with claim 4 wherein the biasing meansis a window shade-type roller supporting the supply roll.
 6. Collectormeans in accordance with claim 1 wherein the absorber plate is mountededgewise adjacent the bottom of a parabolic trough-type reflector means,both sides of said absorber plate are thus exposed to solar rays, likeglazing sheets are mounted on both sides of said absorber plate and thecap is an inverted, generally U-shaped cap with its depending legsextending at least partially over said glazing sheets.
 7. Collectormeans in accordance with claim 1 wherein the absorber plate is afluid-type heat exchange means having tubular channels formed thereinand adapted to carry head exchange fluid.
 8. Collector means inaccordance with claim 1 wherein the outside surface of the cap isreflective to solar rays.